Protocol for Increasing Carotenoid Levels in the Roots of Citrus Plants

Carotenoids in plants play several key functions such as acting as light-harvesters, antioxidants (Lado et al., 2016) or being precursors of strigolactones, abscisic acid, volatiles and other signaling compounds (Arbona et al., 2013). Although those functions are well-known in light-exposed tissues, information in belowground organs is limited because of reduced abundance of these pigments. In order to better understand the role of carotenoids in roots, we developed a methodology to increase the abundance of these pigments in underground tissues. We took advantage of the fact that citrus roots exposed to light develop pigmentation in order to increase the carotenoid content. Therefore, here we describe a simple method to increase carotenoids in citrus roots.